As feature sizes are becoming smaller and smaller, the cleaning of the edge region of the wafer is becoming more difficult. In addition, as newer cleaning techniques are being adapted for the manufacturing process to achieve the smaller feature sizes, there are different process chemistries being utilized for these techniques. Some of these processing chemistries may be corrosive to the active portion of the wafer, i.e., the region of the wafer where the integrated circuits are defined. Another consequence of the shrinking feature sizes is that the edge exclusion zone is becoming smaller. Thus, any cleaning of the edge must be directed to the edge so that the corrosive chemistries do not impact the remainder of the wafer. Currently, techniques are being developed in order to facilitate the cleaning of the edge so that any particulates or contamination can be removed from the processing performed on the substrate. However, there is a need to be able to clean the edge without affecting the center portion of the wafer. As new processes are being used for wafer processing, this need will become more apparent, especially with the use of corrosive processing gases as cleaning chemistries.
Currently when cleaning wafers or the bevel edges of a wafer, the cleaning process is manually controlled. That is, visual inspection of the process through a process window alerts an operator that the plasma used to clean the bevel edge has become unconfined and may affect the actual integrated circuits on the semiconductor substrate. The use of a visual inspection of the process when using a plasma to clean the bevel edge yields unreliable results.
In view of the foregoing, there is a need for systems and methods to reliably monitor the confinement of a plasma when cleaning a bevel edge of a wafer in order to reliably monitor the confinement of the plasma.